Altered brain microstructure assessed by diffusion tensor imaging in patients with diabetes and gastrointestinal symptoms

Symptom perception in adults with chronic physical disease: A systematic review of insular impairments

BACKGROUND

To perform self-care, individuals with a chronic illness must be able to perceive bodily changes (ie., interoception) so they can respond to symptoms when they arise. Interoception is regulated by the insular cortex of the brain. Symptom perception is poor in various physical diseases, which may be associated with impairments in the insular cortex.

OBJECTIVE

The purpose of this study was to explore whether patterns of insular impairment exist among adults with chronic physical diseases and to analyze the relationship with disease-related symptoms.

METHODS

We identified studies that assessed the structure and/or activity of the insula through MRI and/or (f)MRI in adults with chronic physical diseases (vs. healthy controls) by searching five databases. Results are reported as a narrative synthesis.

RESULTS

Fifty studies were conducted to investigate the structure or activity of the insula among adults with diabetes, cancer, heart failure, or chronic pulmonary disease. In 19 studies investigators found that patients with a chronic disease had lower/damaged insular volume/density/thickness than healthy controls or reduced insular blood flow. When insular activity was explored in 22 studies, most investigators reported higher insular activity and lower neural connectivity. Five studies explored the association between insular volume/activity and symptom severity: four reported a positive trend.

CONCLUSION

People with chronic physical diseases have lower insular grey matter volume/density/thickness and abnormal insular activity when compared to healthy people. Insular activity may be related to symptom severity. These results suggest that insular structure and/or activity may explain poor symptom perception.

Quantification of white matter hyperintensities in type 1 diabetes and its relation to neuropathy and clinical characteristics

AIMS

The aims were to quantify periventricular and deep white matter hyperintensities (WMHs) in adults with type 1 diabetes with different neuropathic phenotypes and to correlate WMH measurements to explanatory factors in diabetes.

METHODS

WMH measurements were obtained from brain magnetic resonance imaging of 56 adults with type 1 diabetes in subgroups including painful diabetic peripheral neuropathy (DPN), painless DPN, without DPN and 20 healthy controls using Fazekas scale and automatic segmentation analysis.

RESULTS

No differences in Fazekas assessed WMHs were found (individuals with periventricular lesions: diabetes 66 % vs. controls 40 %, p = 0.063, deep lesions: diabetes 52 % vs. controls 50 %, p = 1.0). Using automatic detection, there were no significant differences in count of periventricular (p = 0.30) or deep (p = 0.31) WMHs. Higher periventricular lesion burden was present in diabetes compared with controls (0.21 % vs. 0.06 %, p = 0.048), which was associated with more severe DPN, increased age, decreased cognitive function, and reduced volumetric and metabolic brain measures (all p < 0.05).

CONCLUSIONS

Our findings indicate increased burden of periventricular WMHs in diabetes which were associated to DPN severity and measurements reflecting neurodegeneration. Deep WMHs, often considered as chronic ischemic, were not significantly different. Mechanisms reflecting neurodegeneration and accelerated brain aging could be an overlooked aspect of peripheral and central neuropathy.

Neuropathic phenotypes of type 1 diabetes are related to different signatures of magnetic resonance spectroscopy-assessed brain metabolites

OBJECTIVES

The study aimed to investigate brain metabolites in type 1 diabetes and the associations with disease characteristics. We explored the metabolic profiles predicting different neuropathic phenotypes using multiple linear regression analyses.

METHODS

We compared brain metabolites in 55 adults with type 1 diabetes (including painful diabetic peripheral neuropathy (DPN), painless DPN, without DPN) with 20 healthy controls. Proton magnetic resonance spectroscopy measurements (N-acetylaspartate (NAA), glutamate (glu), myo-inositol (mI), and glycerophosphocholine (GPC) were obtained in ratios to creatine (cre)) from the parietal region, anterior cingulate cortex and thalamus.

RESULTS

The overall diabetes group revealed decreased parietal NAA/cre compared to healthy controls (1.41 ± 0.12 vs. 1.55 ± 0.13,p < 0.001) and increased mI/cre (parietal: 0.62 ± 0.08 vs. 0.57 ± 0.07,p = 0.025, cingulate: 0.65 ± 0.08 vs. 0.60 ± 0.08,p = 0.033). Reduced NAA/cre was associated with more severe DPN (all p ≤ 0.04) whereas increased mI/cre was associated with higher hemoglobin A1c (HbA1c) (p = 0.02). Diabetes was predicted from decreased parietal NAA/cre, increased parietal ml/cre, and decreased thalamic glu/cre. DPN was predicted from decreased parietal NAA/cre and increased GPC/cre. Painful DPN was predicted from increased parietal GPC/cre and thalamic glu/cre.

CONCLUSIONS

Specific metabolic brain profiles were linked to the different phenotypes of diabetes, DPN and painful DPN.

SIGNIFICANCE

Assessment of metabolic profiles could be relevant for detailed understanding of central neuropathy in diabetes.

Rate of abnormalities in quantitative MR neuroimaging of persons with chronic traumatic brain injury

BACKGROUND

Mild traumatic brain injury (mTBI) can result in lasting brain damage that is often too subtle to detect by qualitative visual inspection on conventional MR imaging. Although a number of FDA-cleared MR neuroimaging tools have demonstrated changes associated with mTBI, they are still under-utilized in clinical practice.

METHODS

We investigated a group of 65 individuals with predominantly mTBI (60 mTBI, 48 due to motor-vehicle collision, mean age 47 ± 13 years, 27 men and 38 women) with MR neuroimaging performed in a median of 37 months post-injury. We evaluated abnormalities in brain volumetry including analysis of left-right asymmetry by quantitative volumetric analysis, cerebral perfusion by pseudo-continuous arterial spin labeling (PCASL), white matter microstructure by diffusion tensor imaging (DTI), and neurometabolites via magnetic resonance spectroscopy (MRS).

RESULTS

All participants demonstrated atrophy in at least one lobar structure or increased lateral ventricular volume. The globus pallidi and cerebellar grey matter were most likely to demonstrate atrophy and asymmetry. Perfusion imaging revealed significant reductions of cerebral blood flow in both occipital and right frontoparietal regions. Diffusion abnormalities were relatively less common though a subset analysis of participants with higher resolution DTI demonstrated additional abnormalities. All participants showed abnormal levels on at least one brain metabolite, most commonly in choline and N-acetylaspartate.

CONCLUSION

We demonstrate the presence of coup-contrecoup perfusion injury patterns, widespread atrophy, regional brain volume asymmetry, and metabolic aberrations as sensitive markers of chronic mTBI sequelae. Our findings expand the historic focus on quantitative imaging of mTBI with DTI by highlighting the complementary importance of volumetry, arterial spin labeling perfusion and magnetic resonance spectroscopy neurometabolite analyses in the evaluation of chronic mTBI.

Central nervous system microstructural alterations in Type 1 diabetes mellitus: A systematic review of diffusion Tensor imaging studies

AIMS

Type 1 diabetes mellitus (T1DM) is a chronic childhood disease with potentially persistent CNS disruptions. In this study, we aimed to systematically review diffusion tensor imaging studies in patients with T1DM to understand the microstructural effects of this entity on individuals' brains METHODS: We performed a systematic search and reviewed the studies to include the DTI studies in individuals with T1DM. The data for the relevant studies were extracted and a qualitative synthesis was performed.

RESULTS

A total of 19 studies were included, most of which showed reduced FA widespread in optic radiation, corona radiate, and corpus callosum, as well as other frontal, parietal, and temporal regions in the adult population, while most of the studies in the juvenile patients showed non-significant differences or a non-persistent pattern of changes. Also, reduced AD and MD in individuals with T1DM compared to controls and non-significant differences in RD were noted in the majority of studies. Microstructural alterations were associated with clinical profile, including age, hyperglycemia, diabetic ketoacidosis and cognitive performance.

CONCLUSION

T1DM is associated with microstructural brain alterations including reduced FA, MD, and AD in widespread brain regions, especially in association with glycemic fluctuations and in adult age.

The Retinal Nerve Fiber Layer Thickness Is Associated with Systemic Neurodegeneration in Long-Term Type 1 Diabetes

Purpose

To determine whether the retinal nerve fiber layer thickness can be used as an indicator for systemic neurodegeneration in diabetes.

Methods

We used existing data from 38 adults with type 1 diabetes and established polyneuropathy. Retinal nerve fiber layer thickness values of four scanned quadrants (superior, inferior, temporal, and nasal) and the central foveal thickness were extracted directly from optical coherence tomography. Nerve conduction velocities were recorded using standardized neurophysiologic testing of the tibial and peroneal motor nerves and the radial and median sensory nerves, 24-hour electrocardiographic recordings were used to retrieve time- and frequency-derived measures of heart rate variability, and a pain catastrophizing scale was used to assess cognitive distortion.

Results

When adjusted for hemoglobin A1c, the regional thickness of the retinal nerve fiber layers was (1) positively associated with peripheral nerve conduction velocities of the sensory and motor nerves (all P < 0.036), (2) negatively associated with time and frequency domains of heart rate variability (all P < 0.033), and (3) negatively associated to catastrophic thinking (all P < 0.038).

Conclusions

Thickness of the retinal nerve fiber layer was a robust indicator for clinically meaningful measures of peripheral and autonomic neuropathy and even for cognitive comorbidity.

Translational Relevance

The findings indicate that the thickness of the retinal nerve fiber layer should be studied in adolescents and people with prediabetes to determine whether it is useful to predict the presence and severity of systemic neurodegeneration.

Differences in brain activity between normal and diabetic rats under isoflurane anesthesia: a resting-state functional MRI study

BACKGROUND

Altered neural activity based on the fractional amplitude of low-frequency fluctuations (fALFF) has been reported in patients with diabetes. However, whether fALFF can differentiate healthy controls from diabetic animals under anesthesia remains unclear. The study aimed to elucidate the changes in fALFF in a rat model of diabetes under isoflurane anesthesia.

METHODS

The first group of rats (n = 5) received a single intraperitoneal injection of 70 mg/kg streptozotocin (STZ) to cause the development of diabetes. The second group of rats (n = 7) received a single intraperitoneal injection of the same volume of solvent. Resting-state functional magnetic resonance imaging was used to assess brain activity at 4 weeks after STZ or solvent administration.

RESULTS

Compared to the healthy control animals, rats with diabetes showed significantly decreased fALFF in various brain regions, including the cingulate cortex, somatosensory cortex, insula, and striatum (all P < 0.05). The decreased fALFF suggests the aberrant neural activities in the diabetic rats. No regions were detected in which the control group had a lower fALFF than that in the diabetes group.

CONCLUSIONS

The results of this study demonstrated that the fALFF could be used to differentiate healthy controls from diabetic animals, providing meaningful information regarding the neurological pathophysiology of diabetes in animal models.

Central neuronal transmission in response to tonic cold pain is modulated in people with type 1 diabetes and severe polyneuropathy

AIMS

This study aimed to investigate cortical source activity and identify source generators in people with type 1 diabetes during rest and tonic cold pain.

METHODS

Forty-eight participants with type 1 diabetes and neuropathy, and 21 healthy controls were investigated with electroencephalography (EEG) during 5-minutes resting and 2-minutes tonic cold pain (immersing the hand into water at 2 °C). EEG power was assessed in eight frequency bands, and EEG source generators were analyzed using standardized low-resolution electromagnetic tomography (sLORETA).

RESULTS

Compared to resting EEG, cold pain EEG power differed in all bands in the diabetes group (all p < 0.001) and six bands in the controls (all p < 0.05). Source generator activity in the diabetes group was increased in delta, beta2, beta3, and gamma bands and decreased in alpha1 (all p < 0.006) with changes mainly seen in the frontal and limbic lobe. Compared to controls, people with diabetes had decreased source generator activity during cold pain in the beta2 and beta3 bands (all p < 0.05), mainly in the frontal lobe.

CONCLUSIONS

Participants with type 1 diabetes had altered EEG power and source generator activity predominantly in the frontal and limbic lobe during tonic cold pain. The results may indicate modulated central transmission and neuronal impairment.

Diabetic Neuropathy Influences Control of Spinal Mechanisms

PURPOSE

Comprehensive evaluation of the upstream sensory processing in diabetic symmetrical polyneuropathy (DSPN) is sparse. The authors investigated the spinal nociceptive withdrawal reflex and the related elicited somatosensory evoked cortical potentials. They hypothesized that DSPN induces alterations in spinal and supraspinal sensory-motor processing compared with age- and gender-matched healthy controls.

METHODS

In this study, 48 patients with type 1 diabetes and DSPN were compared with 21 healthy controls. Perception and reflex thresholds were determined and subjects received electrical stimulations on the plantar site of the foot at three stimulation intensities to evoke a nociceptive withdrawal reflex. Electromyogram and EEG were recorded for analysis.

RESULTS

Patients with DSPN had higher perception (P < 0.001) and reflex (P = 0.012) thresholds. Fewer patients completed the recording session compared with healthy controls (34/48 vs. 21/21; P = 0.004). Diabetic symmetrical polyneuropathy reduced the odds ratio of a successful elicited nociceptive withdrawal reflex (odds ratio = 0.045; P = 0.014). Diabetic symmetrical polyneuropathy changed the evoked potentials (F = 2.86; P = 0.025), and post hoc test revealed reduction of amplitude (-3.72 mV; P = 0.021) and prolonged latencies (15.1 ms; P = 0.013) of the N1 peak.

CONCLUSIONS

The study revealed that patients with type 1 diabetes and DSPN have significantly changed spinal and supraspinal processing of the somatosensory input. This implies that DSPN induces widespread differences in the central nervous system processing of afferent A-δ and A-β fiber input. These differences in processing may potentially lead to identification of subgroups with different stages of small fiber neuropathy and ultimately differentiated treatments.

Gastroparesis and functional dyspepsia: different diseases or different ends of the spectrum?

PURPOSE OF REVIEW

This review assesses the relationship between gastroparesis and functional dyspepsia, in light of recent research assessing cause, pathophysiology and treatment.

RECENT FINDINGS

The Gastroparesis Cardinal Symptom Index (GCSI) lacks the ability to readily distinguish functional dyspepsia from gastroparesis based on symptoms. Although prior studies found that the extent of delay in gastric emptying did not accurately predict severity of symptoms, when optimally measured, delayed gastric emptying may in fact correlate with gastroparesis symptoms. Enteric dysmotility may be an important risk factor for gastroparesis. Altered central processing may play a role in symptom generation for both gastroparesis and functional dyspepsia based on functional brain MRI. Treatment directed towards reducing low-grade inflammation and improving mucosal barrier function in the duodenum may represent a novel therapeutic target for functional dyspepsia, whereas gastric peroral endoscopy myotomy (G-POEM) remains a promising intervention for refractory gastroparesis.

SUMMARY

Abnormalities on functional MRI of the brain have been identified in patients with functional dyspepsia and gastroparesis. Small bowel dysmotility and duodenal barrier dysfunction have been implicated in the pathophysiology of gastroparesis and functional dyspepsia, respectively. New treatments for functional dyspepsia may target low-grade duodenal inflammation and barrier dysfunction. The pylorus remains a target in gastroparesis.

Altered functional connectivity of the posterior cingulate cortex in type 2 diabetes with cognitive impairment

The posterior cingulate cortex (PCC) has been suggested to be a cortical hub of the default mode network (DMN). Our goal in the current study was to determine whether there were alterations in the PCC's functional connectivity (FC) with whole brain regions in type 2 diabetes mellitus (T2DM) and to determine their relationships with cognitive dysfunction. In this study, the FC of the PCC was characterized by using resting-state functional MRI and a seed-based whole-brain correlation method in 24 T2DM patients and compared with 24 well-matched healthy controls. Spearman correlation analysis was performed to determine the relationships between the FC of the PCC and cognitive dysfunction. T2DM was associated with a significantly decreased FC of the PCC to widespread brain regions (p < 0.05, corrected for AlphaSim). We also found that the FC of the PCC in these brain regions was positively correlated with several neuropsychological test scores, such as the FC to the right angular gyrus (AnG) and the bilateral middle temporal gyrus (MTG) with the Auditory Verbal Learning Test (AVLT) and the FC to the bilateral inferior frontal gyrus (IFG) with the digit span test (DST). Moreover, the FCs of the PCC to the right superior parietal lobule (SPL), bilateral temporal lobes and left cerebrum were detected as negatively correlated with the Trail Making Test (TMT). No such correlations were detected in healthy controls. The present study provides useful information about the effect of the FC of the PCC on the underlying neuropathological process of T2DM-related cognitive dysfunction and may provide supporting evidence for further molecular biology studies.

Status of Brain Imaging in Gastroparesis

The pathophysiology of nausea and vomiting in gastroparesis is complicated and multifaceted involving the collaboration of both the peripheral and central nervous systems. Most treatment strategies and studies performed in gastroparesis have focused largely on the peripheral effects of this disease, while our understanding of the central nervous system mechanisms of nausea in this entity is still evolving. The ability to view the brain with different neuroimaging techniques has enabled significant advances in our understanding of the central emetic reflex response. However, not enough studies have been performed to further explore the brain–gut mechanisms involved in nausea and vomiting in patients with gastroparesis. The purpose of this review article is to assess the current status of brain imaging and summarize the theories about our present understanding on the central mechanisms involved in nausea and vomiting (N/V) in patients with gastroparesis. Gaining a better understanding of the complex brain circuits involved in the pathogenesis of gastroparesis will allow for the development of better antiemetic prophylactic and treatment strategies.

Differences between normal and diabetic brains in middle-aged rats by MRI

Normal aging is a risk factor for metabolic disorders such as diabetes, and diabetes is also a recognized cause of accelerated aging. Being able to distinguish changes caused by normal aging from those caused by diabetes, would provide insight into how the aging brain interacts with diabetes. Eight types of MRI metric maps (magnetization relaxation time constants of T1 and T2, cerebral blood flow, cerebrovascular permeability, mean diffusivity, diffusion fractional anisotropy, mean diffusion kurtosis and diffusion directional entropy) were generated for all rats from the three groups of normal young, healthy and 1.5-month diabetic middle-aged rats under investigation. Measurements of multiple MRI indices of cerebral white and gray matter from animals of the three groups provide complementary results and insight into differences between healthy and diabetic white / gray matter in the mid-aged rats. Our data indicate that MRI may distinguish between the normal and diabetes in mid-aged rat brains by measuring either T1 and T2 of gray matter, or fractional anisotropy of white matter and gray matter. Therefore, MRI can distinguish changes of cerebral tissue due to the normal aging from diabetic aging, which may lead to be able to better understand how diabetes accelerates aging in normal brain.

Diabetic Gastroparesis

This review covers the epidemiology, pathophysiology, clinical features, diagnosis, and management of diabetic gastroparesis, and more broadly diabetic gastroenteropathy, which encompasses all the gastrointestinal manifestations of diabetes mellitus. Up to 50% of patients with type 1 and type 2 DM and suboptimal glycemic control have delayed gastric emptying (GE), which can be documented with scintigraphy, 13C breath tests, or a wireless motility capsule; the remainder have normal or rapid GE. Many patients with delayed GE are asymptomatic; others have dyspepsia (i.e., mild to moderate indigestion, with or without a mild delay in GE) or gastroparesis, which is a syndrome characterized by moderate to severe upper gastrointestinal symptoms and delayed GE that suggest, but are not accompanied by, gastric outlet obstruction. Gastroparesis can markedly impair quality of life, and up to 50% of patients have significant anxiety and/or depression. Often the distinction between dyspepsia and gastroparesis is based on clinical judgement rather than established criteria. Hyperglycemia, autonomic neuropathy, and enteric neuromuscular inflammation and injury are implicated in the pathogenesis of delayed GE. Alternatively, there are limited data to suggest that delayed GE may affect glycemic control. The management of diabetic gastroparesis is guided by the severity of symptoms, the magnitude of delayed GE, and the nutritional status. Initial options include dietary modifications, supplemental oral nutrition, and antiemetic and prokinetic medications. Patients with more severe symptoms may require a venting gastrostomy or jejunostomy and/or gastric electrical stimulation. Promising newer therapeutic approaches include ghrelin receptor agonists and selective 5-hydroxytryptamine receptor agonists.

Liraglutide treatment reduced interleukin-6 in adults with type 1 diabetes but did not improve established autonomic or polyneuropathy

AIMS

Type 1 diabetes can be complicated with neuropathy that involves immune-mediated and inflammatory pathways. Glucagon-like peptide-1 receptor agonists such as liraglutide, have shown anti-inflammatory properties, and thus we hypothesized that long-term treatment with liraglutide induced diminished inflammation and thus improved neuronal function.

METHODS

The study was a randomized, double-blinded, placebo-controlled trial of adults with type 1 diabetes and confirmed symmetrical polyneuropathy. They were randomly assigned (1:1) to receive either liraglutide or placebo. Titration was 6 weeks to 1.2-1.8 mg/d, continuing for 26 weeks. The primary endpoint was change in latency of early brain evoked potentials. Secondary endpoints were changes in proinflammatory cytokines, cortical evoked potential, autonomic function and peripheral neurophysiological testing.

RESULTS

Thirty-nine patients completed the study, of whom 19 received liraglutide. In comparison to placebo, liraglutide reduced interleukin-6 (-22.6%; 95% confidence interval [CI]: -38.1, -3.2; P = .025) with concomitant numerical reductions in other proinflammatory cytokines. However neuronal function was unaltered at the central, autonomic or peripheral level. Treatment was associated with -3.38 kg (95% CI: -5.29, -1.48; P < .001] weight loss and a decrease in urine albumin/creatinine ratio (-40.2%; 95% CI: -60.6, -9.5; P = .02).

CONCLUSION

Hitherto, diabetic neuropathy has no cure. Speculations can be raised whether mechanism targeted treatment, e.g. lowering the systemic level of proinflammatory cytokines may lead to prevention or treatment of the neuroinflammatory component in early stages of diabetic neuropathy. If ever successful, this would serve as an example of how fundamental mechanistic principles are translated into clinical practice similar to those applied in the cardiovascular and nephrological clinic.

Deterioration of Brain Neural Tracts in Elderly Women with Sarcopenia

OBJECTIVES

Sarcopenia is known to be associated with increased stiffness in brain arteries, which causes deterioration in brain structure and function. In this study, the authors evaluated the deterioration of neural tracts using diffusion tensor tractography (DTT) in elderly women with sarcopenia and investigated whether deterioration of neural tracts is consistent with clinical findings.

METHODS

Twenty elderly women with sarcopenia were recruited. Muscle mass was measured by dual energy x-ray absorptiometry. Hand-grip power and gait speed were also assessed. Memory function was evaluated using the Seoul Neuropsychological Screening Battery. Additionally, using DTT-Studio software, the authors evaluated eight neural tracts: the corticospinal tract (CST), corticoreticular pathway, fornix, cingulum, superior longitudinal fasciculus, inferior longitudinal fasciculus, inferior fronto-occipital fasciculus, and optic radiation. The authors measured the DTT parameters (fractional anisotropy [FA] and fiber volume [FV]) for each neural tract.

RESULTS

The FA and FV values were decreased in all the evaluated neural tracts, compared with those of the 20 normal comparison subjects. The FVs of the CST were significantly correlated with the hand-grip power of elderly women with sarcopenia. The FVs of the fornix and cingulum in elderly women with sarcopenia were significantly correlated with their memory function.

CONCLUSION

The authors found that the neural tracts in elderly women with sarcopenia were extensively deteriorated, and their hand-grip power and memory function were associated with related neural tracts. The DTT seems to be a useful tool for evaluating structural changes in the brains of people with sarcopenia.

Brain spectroscopy reveals that N-acetylaspartate is associated to peripheral sensorimotor neuropathy in type 1 diabetes

AIMS

Emerging evidence shows, that distal symmetric peripheral neuropathy (DSPN) also involves alterations in the central nervous system. Hence, the aims were to investigate brain metabolites in white matter of adults with diabetes and DSPN, and to compare any cerebral disparities with peripheral nerve characteristics.

METHODS

In type 1 diabetes, brain metabolites of 47 adults with confirmed DSPN were compared with 28 matched healthy controls using proton magnetic resonance spectroscopy (H-MRS) in the parietal region including the sensorimotor fiber tracts.

RESULTS

Adults with diabetes had 9.3% lower ratio of N-acetylaspartate/creatine (NAA/cre) in comparison to healthy (p < 0.001). Lower NAA/cre was associated with lower sural (p = 0.01) and tibial (p = 0.04) nerve amplitudes, longer diabetes duration (p = 0.03) and higher age (p = 0.03). In addition, NAA/cre was significantly lower in the subgroup with proliferative retinopathy as compared to the subgroup with non-proliferative retinopathy (p = 0.02).

CONCLUSIONS

The association to peripheral nerve dysfunction, indicates concomitant presence of DSPN and central neuropathies, supporting the increasing recognition of diabetic neuropathy being, at least partly, a disease leading to polyneuropathy. Decreased NAA, is a potential promising biomarker of central neuronal dysfunction or loss, and thus may be useful to measure progression of neuropathy in diabetes or other neurodegenerative diseases.

Type 1 diabetic patients with peripheral neuropathy have pan-enteric prolongation of gastrointestinal transit times and an altered caecal pH profile

AIMS/HYPOTHESIS

We hypothesised that type 1 diabetic patients with established diabetic sensorimotor polyneuropathy (DSPN) would have segmental and/or pan-enteric dysmotility in comparison to healthy age-matched controls. We aimed to investigate the co-relationships between gastrointestinal function, degree of DSPN and clinical symptoms.

METHODS

An observational comparison was made between 48 patients with DSPN (39 men, mean age 50 years, range 29-71 years), representing the baseline data of an ongoing clinical trial (representing a secondary analysis of baseline data collected from an ongoing double-blind randomised controlled trial investigating the neuroprotective effects of liraglutide) and 41 healthy participants (16 men, mean age 49 years, range 30-78) who underwent a standardised wireless motility capsule test to assess gastrointestinal transit. In patients, vibration thresholds, the Michigan Neuropathy Screening Instrument and Patient Assessment of Upper Gastrointestinal Symptom questionnaires were recorded.

RESULTS

Compared with healthy controls, patients showed prolonged gastric emptying (299 ± 289 vs 179 ± 49 min; p = 0.01), small bowel transit (289 ± 107 vs 224 ± 63 min; p = 0.001), colonic transit (2140, interquartile range [IQR] 1149-2799 min vs 1087, IQR 882-1650 min; p = 0.0001) and whole-gut transit time (2721, IQR 1196-3541 min vs 1475 (IQR 1278-2214) min; p < 0.0001). Patients also showed an increased fall in pH across the ileocaecal junction (-1.8 ± 0.4 vs -1.3 ± 0.4 pH; p < 0.0001), which was associated with prolonged colonic transit (r = 0.3, p = 0.001). Multivariable regression, controlling for sex, disease duration and glycaemic control, demonstrated an association between whole-gut transit time and total GCSI (p = 0.02).

CONCLUSIONS/INTERPRETATION

Pan-enteric prolongation of gastrointestinal transit times and a more acidic caecal pH, which may represent heightened caecal fermentation, are present in patients with type 1 diabetes. The potential implication of delayed gastrointestinal transit on the bioavailability of nutrition and on pharmacotherapeutic and glycaemic control warrants further investigation.

TRIAL REGISTRATION

EUDRA CT: 2013-004375-12.

Integrity of central nervous function in diabetes mellitus assessed by resting state EEG frequency analysis and source localization

Diabetes mellitus (DM) is associated with structural and functional changes of the central nervous system. We used electroencephalography (EEG) to assess resting state cortical activity and explored associations to relevant clinical features. Multichannel resting state EEG was recorded in 27 healthy controls and 24 patients with longstanding DM and signs of autonomic dysfunction. The power distribution based on wavelet analysis was summarized into frequency bands with corresponding topographic mapping. Source localization analysis was applied to explore the electrical cortical sources underlying the EEG. Compared to controls, DM patients had an overall decreased EEG power in the delta (1-4Hz) and gamma (30-45Hz) bands. Topographic analysis revealed that these changes were confined to the frontal region for the delta band and to central cortical areas for the gamma band. Source localization analysis identified sources with reduced activity in the left postcentral gyrus for the gamma band and in right superior parietal lobule for the alpha1 (8-10Hz) band. DM patients with clinical signs of autonomic dysfunction and gastrointestinal symptoms had evidence of altered resting state cortical processing. This may reflect metabolic, vascular or neuronal changes associated with diabetes.

Ravages of Diabetes on Gastrointestinal Sensory-Motor Function: Implications for Pathophysiology and Treatment

Symptoms related to functional and sensory abnormalities are frequently encountered in patients with diabetes mellitus. Most symptoms are associated with impaired gastric and intestinal function. In this review, we discuss basic concepts of sensory-motor dysfunction and how they relate to clinical findings and gastrointestinal abnormalities that are commonly seen in diabetes. In addition, we review techniques that are available for investigating the autonomic nervous system, neuroimaging and neurophysiology of sensory-motor function. Such technological advances, while not readily available in the clinical setting, may facilitate stratification and individualization of therapy in diabetic patients in the future. Unraveling the structural, mechanical, and sensory remodeling in diabetes disease is based on a multidisciplinary approach that can bridge the knowledge from a variety of scientific disciplines. The final goal is to increase the understanding of the damage to GI structures and to sensory processing of symptoms, in order to assist clinicians with developing an optimal mechanics based treatment.

Gray matter alterations and correlation of nutritional intake with the gray matter volume in prediabetes

The neurophysiology of prediabetes plays an important role in preventive medicine. The dysregulation of glucose metabolism is likely linked to changes in neuron-related gray matter. Therefore, we designed this study to investigate gray matter alterations in medication-naive prediabetic patients. We expected to find alterations in the gray matter of prediabetic patients.A total of 64 prediabetic patients and 54 controls were enrolled. All subjects received T1 scans using a 3-T magnetic resonance imaging machine. Subjects also completed nutritional intake records at the 24-hour and 3-day time points to determine their carbohydrate, protein, fat, and total calorie intake. We utilized optimized voxel-based morphometry to estimate the gray matter differences between the patients and controls. In addition, the preprandial serum glucose level and the carbohydrate, protein, fat, and total calorie intake levels were tested to determine whether these parameters were correlated with the gray matter volume.Prediabetic patients had lower gray matter volumes than controls in the right anterior cingulate gyrus, right posterior cingulate gyrus, left insula, left super temporal gyrus, and left middle temporal gyrus (corrected P < 0.05; voxel threshold: 33). Gray matter volume in the right anterior cingulate was also negatively correlated with the preprandial serum glucose level gyrus in a voxel-dependent manner (r = -0.501; 2-tailed P = 0.001).The cingulo-temporal and insula gray matter alterations may be associated with the glucose dysregulation in prediabetic patients.

Brain changes in diabetes mellitus patients with gastrointestinal symptoms

Diabetes mellitus is a common disease and its prevalence is increasing worldwide. In various studies up to 30%-70% of patients present dysfunction and complications related to the gut. To date several clinical studies have demonstrated that autonomic nervous system neuropathy and generalized neuropathy of the central nervous system (CNS) may play a major role. This systematic review provides an overview of the neurodegenerative changes that occur as a consequence of diabetes with a focus on the CNS changes and gastrointestinal (GI) dysfunction. Animal models where diabetes was induced experimentally support that the disease induces changes in CNS. Recent investigations with electroencephalography and functional brain imaging in patients with diabetes confirm these structural and functional brain changes. Encephalographic studies demonstrated that altered insular processing of sensory stimuli seems to be a key player in symptom generation. In fact one study indicated that the more GI symptoms the patients experienced, the deeper the insular electrical source was located. The electroencephalography was often used in combination with quantitative sensory testing mainly showing hyposensitivity to stimulation of GI organs. Imaging studies on patients with diabetes and GI symptoms mainly showed microstructural changes, especially in brain areas involved in visceral sensory processing. As the electrophysiological and imaging changes were associated with GI and autonomic symptoms they may represent a future therapeutic target for treating diabetics either pharmacologically or with neuromodulation.

Alterations of neocortico-limbic association fibers and correlation with diet in prediabetes diagnosed by impaired fasting glucose

PURPOSE

To assess the existence of alterations in the micro-integrity of the fasciculus in prediabetic subjects. The issue of micro-integrity in white matter tracts has not been adequately addressed in prediabetes.

MATERIALS AND METHODS

Sixty-four prediabetic subjects and 54 controls were enrolled. All participants completed 24-hour diet records and 3-day diet records and received diffusion tensor imaging at 3T. The data for white matter micro-integrity were analyzed and compared between prediabetic subjects and controls with age and gender as covariates. In addition, voxel-wise regression between white matter micro-integrity, diet, and preprandial glucose levels were used to explore the relationship between white matter micro-integrity and diet or serum glucose levels.

RESULTS

We found that prediabetic subjects had significant reductions in the micro-integrity of bilateral anterior thalamic radiation, left inferior longitudinal fasciculus, and left superior longitudinal fasciculus (corrected P < 0.05). In addition, total carbohydrate intake amount and preprandial serum glucose levels were negatively correlated with the micro-integrity in the left inferior longitudinal fasciculus and left anterior thalamic radiation (r: -0.47, corrected P < 0.05).

CONCLUSION

Restrictive alterations in the white matter micro-integrity of the anterior thalamic radiation and inferior and superior longitudinal fasciculi might represent the initial "hot spots" for white matter tract alterations, which might play a role in the development of prediabetes. J. Magn. Reson. Imaging 2016;43:1500-1506.

Current understanding of the neuropathophysiology of pain in chronic pancreatitis

Chronic pancreatitis (CP) is a chronic inflammatory disease of the pancreas. The main symptom of patients with CP is chronic and severe abdominal pain. However, the pathophysiology of pain in CP remains obscure. Traditionally, researchers believed that the pain was caused by anatomical changes in pancreatic structure. However, treatment outcomes based on such beliefs are considered unsatisfactory. The emerging explanations of pain in CP are trending toward neurobiological theories. This article aims to review current evidence regarding the neuropathophysiology of pain in CP and its potential implications for the development of new treatments for pain in CP.

Surgical Management of Chronic Pancreatitis

Advances over the past decade have indicated that a complex interplay between environmental factors, genetic predisposition, alcohol abuse, and smoking lead towards the development of chronic pancreatitis. Chronic pancreatitis is a complex disorder that causes significant and chronic incapacity in patients and a substantial burden on the society. Major advances have been made in the etiology and pathogenesis of this disease and the role of genetic predisposition is increasingly coming to the fore. Advances in noninvasive diagnostic modalities now allow for better diagnosis of chronic pancreatitis at an early stage of the disease. The impact of these advances on surgical treatment is beginning to emerge, for example, patients with certain genetic predispositions may be better treated with total pancreatectomy versus lesser procedures. Considerable controversy remains with respect to the surgical management of chronic pancreatitis. Modern understanding of the neurobiology of pain in chronic pancreatitis suggests that a window of opportunity exists for effective treatment of the intractable pain after which central sensitization can lead to an irreversible pain syndrome in patients with chronic pancreatitis. Effective surgical procedures exist for chronic pancreatitis; however, the timing of surgery is unclear. For optimal treatment of patients with chronic pancreatitis, close collaboration between a multidisciplinary team including gastroenterologists, surgeons, and pain management physicians is needed.

Association between visceral, cardiac and sensorimotor polyneuropathies in diabetes mellitus

AIMS

Gastrointestinal complaints are common in diabetes mellitus. However, its association to peripheral sensorimotor and autonomic neuropathies is not well investigated. The aim was to assess skin, muscle, bone and visceral sensitivity in diabetes patients with sensorimotor neuropathy, and correlate these with gastrointestinal symptoms and degree of cardiac autonomic neuropathy.

METHODS

Twenty patients with sensorimotor neuropathy (65% type 2 diabetes, aged 58.3±12.0 years, diabetes duration 15.8±10.0 years) and 16 healthy controls were recruited. Cutaneous sensitivity to von Frey filaments, mechanical allodynia, muscle/bone/rectosigmoid sensitivities, and heart rate variability were examined. Gastrointestinal symptom scores (PAGI-SYM) and health-related quality of life (SF-36) were also recorded.

RESULTS

Patients displayed hypesthesia to von Frey filaments (p=0.028), but no difference to muscle and bone pain sensitivities. Also, patients were hyposensitive to multimodal rectal stimulations (all p<0.05), although they suffered more gastrointestinal complaints. Heart rate variability was reduced in the patient cohort. Rectal mechanical and cutaneous sensitivities correlated (p<0.001), and both were associated with heart rate variability as well as PAGI-SYM and SF-36 scores (p<0.01).

CONCLUSIONS

In diabetic sensorimotor neuropathy there is substantial evidence of concomitant cutaneous, cardiac and visceral autonomic neuropathies. The neuropathy may reduce quality of life and explain the higher prevalence of gastrointestinal complaints.

Do patients with functional chest pain have neuroplastic reorganization of the pain matrix? A diffusion tensor imaging study

Background and aims

In functional chest pain (FCP) of presumed esophageal origin central nervous system hyperexcitability is generally believed to play an important role in pain pathogenesis. However, this theory has recently been challenged. Using magnetic resonance diffusion tensor imaging, the aim was to characterize any microstructural reorganization of the pain neuromatrix in FCP patients.

Methods

13 FCP patients and 20 matched healthy controls were studied in a 3T MR scanner. Inclusion criteria were relevant chest pain, normal coronary angiogram and normal upper gastrointestinal evaluation. Apparent diffusion coefficient (ADC) (i.e. mean diffusivity of water) and fractional anisotropy (FA) (i.e. directionality of water diffusion as a measure of fiber organization) values were assessed in the secondary sensory cortex, cingulate cortex, insula, prefrontal cortex, and amygdala.

Results

Overall, including all regions, no difference in ADC and FA values was found between the patients and controls (P = 0.79 and P = 0.23, respectively). Post-hoc tests revealed no difference in ADC and FA values of the individual regions. However, a trend of patients having increased ADC in the mid insula grey matter and increased FA in the mid insula white matter was observed (both P = 0.065).

Conclusions

This explorative study suggests that microstructural reorganization of the central pain neuromatrix may not be present in well-characterized FCP patients.

Implications

This finding, together with recent neurophysiologal evidence, challenges the theory of visceral hypersensitivity due to changes in the central nervous system in FCP patients.

Rectal sensitivity in diabetes patients with symptoms of gastroparesis

In a clinical setting, diabetic autonomic complications (cardiac, gastrointestinal, urogenital, etc.) are often handled as separate entities. We investigated rectal sensitivity to heat, mechanical distension, and electrical stimulations in 20 patients with diabetes and symptoms of gastroparesis, to evaluate the extent of visceral neuronal damage. Furthermore, to evaluate the relation between the nervous structures we examined gastric emptying and cardiac autonomic function with the hypothesis being an association between these. We found that 60% of patients had delayed gastric empting. Rectal hyposensitivity was a general finding as they tolerated 67% higher thermal, 42% more mechanical, and 33% higher electrical current intensity compared to healthy controls. In patients, most heart rate variability parameters were reduced; they reported significantly more gastrointestinal symptoms and a reduced quality of life in all SF-36 domains. Shortened RR interval correlated with reduced rectal temperature sensitivity, and gastric retention rate was negatively associated with symptoms of nausea and vomiting. To conclude, in these patients with signs and symptoms of diabetic gastroparesis, rectal sensitivity was reduced, and heart rate variability was impaired. Thus, we suggest regarding diabetic autonomic neuropathy as a diffuse disorder. Symptoms of widespread autonomic dysfunction and sensory disorders should be expected and treated in these patients.

Diabetes mellitus may induce cardiovascular disease by decreasing neuroplasticity

Neuroplasticity has been defined "the ability of the nervous system to respond to intrinsic or extrinsic stimuli by reorganizing its structure, function and connections". The nervous system monitors and coordinates internal organ function. Thus neuroplasticity may be associated with the pathogenesis of other diseases besides neuropsychiatric diseases. Decreased neuroplasticity is associated with cardiovascular disease (CVD) and a disease related to decreased neuroplasticity may confer a greater CVD risk. Diabetes mellitus (DM) is related to CVD and DM induces decreased neuroplasticity, which is manifested as depression, Alzheimer's disease and diabetic neuropathy. Therefore we conclude that DM may induce CVD by decreasing neuroplasticity.

Pain and chronic pancreatitis: A complex interplay of multiple mechanisms

Despite multiple theories on the pathogenesis of pain in chronic pancreatitis, no uniform and consistently successful treatment strategy exists and abdominal pain still remains the dominating symptom for most patients and a major challenge for clinicians. Traditional theories focussed on a mechanical cause of pain related to anatomical changes and evidence of increased ductal and interstitial pressures. These observations form the basis for surgical and endoscopic drainage procedures, but the outcome is variable and often unsatisfactory. This underscores the fact that other factors must contribute to pathogenesis of pain, and has shifted the focus towards a more complex neurobiological understanding of pain generation. Amongst other explanations for pain, experimental and human studies have provided evidence that pain perception at the peripheral level and central pain processing of the nociceptive information is altered in patients with chronic pancreatitis, and resembles that seen in neuropathic and chronic pain disorders. However, pain due to e.g., complications to the disease and adverse effects to treatment must not be overlooked as an additional source of pain. This review outlines the current theories on pain generation in chronic pancreatitis which is crucial in order to understand the complexity and limitations of current therapeutic approaches. Furthermore, it may also serve as an inspiration for further research and development of methods that can evaluate the relative contribution and interplay of different pain mechanisms in the individual patients, before they are subjected to more or less empirical treatment.

Diabetic autonomic neuropathy affects symptom generation and brain-gut axis

OBJECTIVE

Long-term diabetes leads to severe peripheral, autonomous, and central neuropathy in combination with clinical gastrointestinal symptoms. The brain-gut axis thus expresses a neurophysiological profile, and heart rate variability (HRV) can be correlated with clinical gastrointestinal symptoms.

RESEARCH DESIGN AND METHODS

Fifteen healthy volunteers and 15 diabetic patients (12 with type 1 diabetes) with severe gastrointestinal symptoms and clinical suspicion of autonomic neuropathy were included. Psychophysics and evoked brain potentials were assessed after painful rectosigmoid electrostimulations, and brain activity was modeled by brain electrical source analysis. Self-reported gastrointestinal symptoms (per the Patient Assessment of Upper Gastrointestinal Disorder Severity Symptom Index) and quality of life (SF-36 Short Form Survey) were collected.

RESULTS

Diabetic patients had autonomous neuropathy, evidenced by decreased electrocardiographic R-R interval (P = 0.03) and lower HRV (P = 0.008). Patients were less sensitive to painful stimulation (P = 0.007), had prolonged latencies of evoked potentials (P ≤ 0.001), and showed diminished amplitude of the N2-P2 component in evoked potentials (P = 0.01). There was a caudoanterior shift of the insular brain source (P = 0.01) and an anterior shift of the cingulate generator (P = 0.01). Insular source location was associated with HRV assessments (all P < 0.02), and the shift (expressed in mm) correlated negatively with physical health (P < 0.001) and positively with nausea (P = 0.03) and postprandial fullness (P = 0.03). Cingulate source shift was correlated negatively with physical health (P = 0.005) and positively with postprandial fullness (P ≤ 0.001).

CONCLUSIONS

This study provides evidence for interaction between autonomic neuropathy and peripheral nervous degeneration, as well as changes in dipole sources in diabetic patients with gastrointestinal symptoms. The findings may lead to improved treatment modalities targeting pharmacological neuroprotection or neuromodulation.